This invention relates to a four-wheel drive hybrid vehicle.
JP-A-H10-246134 published by the Japanese Patent Office in 1998 discloses a hybrid vehicle wherein an engine is combined with a motor generator, and the vehicle is driven by either one or both of the engine and motor generator. The combination of the engine and automatic transmission with the motor generator, and the provision of a center differential gear, makes it is possible to realize four-wheel drive.
In this prior art, when regeneration is performed by the motor generator, a forward clutch of the transmission is released, and the regeneration amount from the motor generator is increased.
However, in this prior art, regeneration is performed while the forward clutch of the transmission is released, so the engine must rotate by itself during regeneration, and fuel cut cannot be performed. Hence, a fuel supply is required to maintain the engine rotating, and although the regeneration amount can be increased, fuel consumption performance decreases.
If on the other hand fuel cut is performed while the forward clutch is still engaged and the regeneration is performed, since the engine brake force acting on the vehicle becomes a value corresponding to the torque required to drive the engine and motor generator, it is difficult to control the engine braking force to a suitable value. Further, the vehicle decelerates while the engine and drive wheels are still connected, so regeneration cannot be performed until a very low vehicle speed is reached at which the input shaft rotation speed of the transmission is less than the idle rotation speed of the engine.
Moreover, the construction of the four-wheel drive hybrid vehicle having a mechanical center differential gear is complex.
It is therefore an object of this invention to provide a four-wheel-drive hybrid vehicle having a simple construction. It is a further object of this invention to achieve an optimum engine braking force while increasing the regeneration amount.
In order to achieve above object, this invention provides a hybrid vehicle, including a first drive wheel, a second drive wheel, an automatic transmission, a first motor generator and engine connected to the first drive wheel via the transmission, a second motor generator connected to the second drive wheel, a battery electrically connected to the first and second motor generators, and a controller functioning to determine a running state of the vehicle, determine a charge state of the battery, control the drive force of the engine and the first motor generator based on the running state of the vehicle and the charge state of the battery, and drive the second motor generator using the battery and the power generated by the first motor generator.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.